Lighting off delay machine. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Lighting off delay machine. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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This device is designed to smoothly turn on and delay off the lighting in the premises. Its peculiarity is that in standby mode it practically does not consume energy from the network. This is especially important for rooms that are not visited very often, such as a garage.

A schematic diagram of the automaton offered to the attention of readers is shown in fig. 1. It can be installed instead of the normal light switch. It works as follows. In the initial state, the contacts of the switch SA1 are open and only the leakage currents of the trinistor VS1, as well as the current of the indicator lamp HL' (fractions of a milliampere), flow through the device. The lighting is turned off. When the contacts of the SA1 switch are closed, the supply voltage is supplied to the pulse generator assembled on the unijunction transistor VT2. However, it will not work until the voltage across the capacitor C1, which is charged through the diode VD1 and the resistor R1, reaches a level sufficient to open the transistor VT1. As this transistor turns on, pulses will begin to appear at the output of the generator, shifting in time from the end to the beginning of each half-cycle of the mains voltage. The pulses will open the trinistor VS1. As a result, the voltage on the lighting lamps will begin to gradually increase and after a few seconds it will reach its nominal value.

Automatic lighting off delay

The current flowing through the lamps will also pass through the winding of the relay K1, which will work and block the contacts of the SA1.2 switch with its contacts. In this state, the device can be indefinitely long. To limit the voltage on the relay winding, diodes VD3 - VD5 are connected in parallel with it. The ripple is smoothed out by capacitor C3.

To turn off the lighting, SA1 is moved to the "Off" position. However, the lighting will remain on as long as the voltage across the capacitor C1 is sufficient to keep the transistor VT1 in the open state. As the capacitor is discharged through the resistor R2, the current through the transistor VT1 will begin to gradually decrease, and the pulses at the output of the generator will move away from the beginning of the half-cycle of the mains voltage to its end. As a result, the voltage on the incandescent lamps will decrease and the brightness of their glow will drop. When the current through the lamps becomes less than the holding current of the relay, its contacts will open, the generator will stop working, the trinistor will not open and the lighting lamps will go out completely.

The delay time for turning off the lighting is several minutes and depends on the characteristics of the transistor VT1 and the time constant of the C1R2 circuit. The time to fully turn on the lighting is a few seconds and is determined by the time constant of the R1C1 circuit.

Most of the details of the machine are placed on a printed circuit board made of one-sided foil fiberglass, a sketch of which is shown in fig. 2.

Automatic lighting off delay

You can use transistors KP301A (VT1) and KT117 (A-G) (VT2), trinistor - KU202KN, diode VD1 - KD103A, KD104A, KD521A, KD522A, KD522B and other similar ones, a zener diode - with a stabilization voltage of 12 ... 15 V and operating current not less than 20 mA. Capacitors C1, C3 - K50-24, K53-14, C2 - KLS, KM-5 and similar, resistors - MLT, C2-33. Switch SA1 - P2K, MT-3.

Relay K1 - RES-55 (passport RS4.569.603) with a winding resistance of 95 ohms and a response voltage of about 2,5 V, RES-44 (RS4.569.251 with parallel connection of windings), RES-10 (RS4.524.304) with winding resistance 45 Ohm and RES-9 (RS4.524.203) with winding resistance 30 Ohm. When choosing a relay, it should be borne in mind that its operation current must be less than the current consumed by lighting lamps, and the release current is less than the leakage current of the trinistor. . The diodes themselves, as well as the VD3 diode bridge, must withstand the current consumed by the lamps. When using the diodes indicated in the diagram, the power of the lamps can reach 5 W, and the trinistor does not require a heat sink. In the case of a more powerful load, you will have to use more powerful diodes, and install the trinistor on a heat sink. The capacitance of the capacitor C6 must be increased by two to three times if the resistance of the relay winding is less than 220 ... 3 ohms.

Establishing the machine comes down to setting the time for turning on the lamps (by selecting a resistor R1) and the delay time for turning them off (by selecting a resistor R2 - smoothly and capacitor C1 - roughly). Indicator gas discharge (TN-0,2, TN-0,5, MN-3, etc.) lamp HL' is needed when the machine is placed in a dark room and it is necessary to indicate its location. The resistance of the resistor R'' depends on the type of lamp. If it is necessary to have a smooth manual adjustment of the brightness of the lighting, it is necessary to introduce a resistor R '-100 kOhm (SP-0,4, SP4-3) into the machine by installing it on the front panel. By the way, it can also be combined with the SA1 switch.

As already noted, the machine is turned on instead of the standard switch (contacts X1, X2) in series with the load. When using separate wiring, mains voltage is applied to contacts X2, X3, and the load is connected to sockets XS1.

All elements of the device are under mains voltage, so its design must exclude the possibility of contact with parts during operation. You should be extremely careful when setting up. All replacement of elements, soldering, connection of measuring instruments should be carried out with the device completely disconnected from the mains, for which it is necessary to pull out the plug with which it is connected to the mains.

Author: I. Nechaev, Kursk

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